This invention relates to an ignition timing control arrangement for an outboard motor with an internal combustion engine and more particularly to an improved arrangement for mounting the ignition system.
It is well known in connection with certain types of engines to provide a flywheel magneto in which the flywheel carries a plurality of rotating magnets and which cooperates with a charging coil and a pulser coil for charging and firing an ignition circuit. In accordance with such arrangements, it is frequently the practice to mount the pulser coil on a plate that so that it can detect and signal the position of the crankshaft in order for proper timing of the ignition of the engine.
Also, with four cycle engines is it well known in the art to mount the timing pulley or gear on the output shaft adjacent to the flywheel. The timing pulley rotates with the output shaft and subsequently drives a belt or a chain which in turn drives a cam shaft assembly thereby controlling the intake and exhaust valves for the cylinders of the engine. As shown in the prior art in FIG. 6 it is conventional to mount the flywheel on the outermost portion of the output shaft. It is also conventional to mount the timing pulley on the output shaft between the flywheel and the engine.
As shown in the prior art the pulser coil is located in a recessed area near the outer diameter of the flywheel. This type of configuration is utilized to minimize the overall height of the engine. As is well known, minimizing the height of the engine is desirable in order to minimize the exterior cowling thereby lowering the aerodynamic drag on the associated watercraft.
In order to achieve a lower engine height it is well known in the art to locate the pulser coil in recessed area of the flywheel. A major disadvantage of this type of configuration, however, is that by locating the pulser coil in the flywheel the center of gravity of the flywheel is shifted away from the face of the engine where the output shaft is supported for rotation. By locating the center of gravity on the outside of the shaft the effect of an imbalance in the flywheel is magnified. This imbalance can cause the pulser coil signal improperly thereby causing a misfiring of the engine. Or, in the case of extreme imbalance, the output shaft could plastically deform thereby causing damage to the engine.
Yet another aggravating factor is that the angle of the motor can be changed during the normal tilt and trim operation of the motor. This has the effect of causing greater imbalance when the motor is operated through the full tilt and trim range.
It is therefore, a principal object of this invention to provide an improved mounting arrangement for the ignition system of the engine. More specifically it is an object of the invention to provide an arrangement of the ignition system of the engine that will insure accuracy in the timing of the engine regardless of the changes in the angle of the output shaft.
It is a further object of this invention to provide a mounting structure that for the ignition system of the engine to facilitate a system that will minimize the possibility of flywheel imbalance.
It is a yet another object of the invention to provide a mounting structure that will increase the reliability of the ignition of the engine.
It is still a further object of the invention to provide a structure that improves the durability of the engine.